Thermostatic switch



. Patented May 1 1, 1937 UNITED STATES PATENT OFFICE iiClaims.

This invention relates to thermostatically controlled electric circuitbreaking and making devices and has for its object the provision of anew and improved device of this type.

The thermostatically controlled electric circuit breaking and makingdevices which have been and now are in general use are so constructedthat they operate slowly in the act of opening the circuit. This resultsin sparking at the contacts with the concomitant fusing and destructionof the said contacts. Attempts have been made to build thermostaticallycontrolled electric circuit making and breaking devices which willoperate an as to cause instantaneous breaking of the circult. These,however, are open to the objection that they are comparativelycomplicated, that they are expensive to manufacture and produce. and, inaddition, have certain objectionable structural features. It is anobject of this invention to produce an electrical circuit breaking andmaking thermostat which will operate so as to cause the practicallyinstantaneous breaking of the circuit and yet be comparatively simple inits structure.

Further, thermostatic switches now in general use close slowly once theyhave opened. Where one of the switch contacts is mounted on a re silientarm (as is sometimes the case) and where the switch is part of amechanism subject to vibration (as is often the case) the vibrationcauses intermittent closing of the switch during the period that theswitch elements are returning from the open position to the full closedposition. This results in premature closing of the circuit and insparking with the resultant destruction of the switch contacts andpossible damage to the element which the switch is supposed to protect.It is an object of this inven tion to construct a thermostatic switchwhich will close practically instantaneously.

I attain the above objects by incorporating into an electric switchthermostatically responsive means which when activated will move in twoplanes (preferably one at. right angles to the other) in so forming thesaid thermostatic means that movement thereof will be permitted in oneof the said planes but restrained in the other of the said planes for acertain predetermined period or distance, and in so positioning thethermostatic means with respect to the switch contact elements that themoment the period or point of restraint is passed the thermostatic meanswill instantaneously move a distance sumcient to cause the opening orpermit the closing of 'the switch contacts.

Further, it often happens that the thermostat switch is so positionedwith respect to the device which it is to protect that thethermostatically responsive elements are not properly affected by thethermal changes in the said device. It is an object of this invention toassociate means with a thermostatic switch which will cause the properactivation of the thermostatically responsive elements when necessary nomatter where the said thermostatic switch is positioned relatively tothe said device.

I attain this object by associating with my thermostatic switch anauxiliary heating coil formed of a material which will permit thecurrent for which the device was designed to flow through but which willheat up when an overload current is flowing through the said device andso positioning the said heating coil that it will directly affect thethermostatically responsive elements of the said thermostatic switch.

The inventive concept herein set forth may take many forms. For thepurpose of more clearly disclosing my invention I have shown in thedrawings which form a part hereof and will now describe some of theseforms.

In the said drawings Figure 1 is a perspective view of my thermostaticswitch in the normal or switch closed position. a

Figure 2 is a side view of the switch shown in Figure 1 when inserted inthe pole winding circuit of a motor. The winding circuit and the motorare shown diagrammatically as is also an auxiliary heating coil whichmay be used either in conjunction with or as a component part of mynovel thermostatic switch.

Figure 3 is a top view of the contact carrying end fragment of thethermostatic switch shown in Figure 2.

Figure 4 is a side view of the switch shown in Figure 1 when in theposition it first assumes after being activated as a result of anoverload or thermal change above the safety point in the motor circuit.

Figure 5 is a top view of the contact carrying end fragment of thethermostatic switch shown in Figure 4.

Figure 6 is a side view of the switch shown in Figure 1 when in theswitch open position which it assumes after being activatedas a resultof an overload or thermal change above the safety point in the motorcircuit.-

Figure 7 is a top view of the disclosure in Figure 6.

Figure 8 is a top view of the contact carrying end fragment of theswitch shown in Figure 1 when in the position it assumes during thereturn of normal operating conditions and preparatory to the closing ofthe switch.

Figure 9 is a perspective view of a modification with the full linesshowing the switch elements in the closed position and the dot and dashlines showing the switch elements in the open position.

Figure 10 is a front view of another modification the full lines showingclosed position of the switch elements and the dot and dash linesshowing the position assumed by one of the thermostatic elements whenthe switch is open.

Figure 11 is a top view of the disclosure shown in Figure 10 with theswitch elements in the closed position.

Figure 12 is a view similar to Figure 11 with the switch elements in theopen position, parts being broken away or shown in section for thepurpose of clearness.

Figure 13 is a section on the line I3I3 of Figure 11.

Figure 14 is a perspective view of the thermal member of the switchshown in Figures 10 to 13 inclusive.

Figure 15 is a side view of still another modification with the fulllines showing the switch and thermal elements in the normal or closedposition and the dot and dash lines showing the switch and thermalelements in the open position.

Figure 16 is a top view of the switch shown in Figure 15 with the fulllines showing the switch and tion of the said elements.

Figure 17 is a side view of still another modification with the fulllines showing the position assumed by the switch and thermal elementswhen the switch is open.

Figure 18 is a top view of the disclosure shown lines showing theposiarm I conducting material, and the stop plate 5.

The thermal member 3 is slotted as at I and bent to form the two arms Iand I which are substantially at right angles to each other. In theswitch shown in Figures 1 to 8 inclusive the widest surface of the arm 1lies in the vertical and the widest surface of the arm 8 lies in thehorizontal plane. When affected by heat the arms I and I will move in aplane substantially at right angles to their widest surface with theresult that the arm I will move in the horizontal plane and the arm I inthe vertical plane. The

thermal unit I is made of material which will react after a certainpredetermined fixed temperature is reached.

The arm 'I terminates at its free end in a finger I and the arm I hasformed near the free end thereof a hook II positioned for operativecontact and engagement with the finger I in the manner which willhereinafter be more particularly described. The arm I has attached tothe lower surface thereof and near its free edge the contact point IIwhich is positioned for cooperative contact with the contact point I2attached to the upper surface of the resilient switch arm I.

Suitable wiring connections 20 and 2| are provided for connecting thethermostatic switch I with the wiring circuit of the motor or otherelectric unit which it will control.

My novel thermostatic switch functions as follows:

(Let it be assumed that the thermostatic switch I has been inserted intothe wiring circuit C of the motor M and positioned so as to be affectedby the temperature of the said motor; and let it be further assumed thatthe themestatic member I'is made of material which will be activatedwhen the temperature of the motor or motor circuit reaches a point at orJust above result that the arm I will tend to move inwardly from theposition shown in Figure 3 to that shown in Figures 5 and 7 .while thearm I will tend to move upwardly from the position shown in Figures 1and 2 to that shown in Figures 4 and 6. As the arm I moves upwardly itwill be followed by the resilient arm 4 contacts with the stop plate I,a position shown in Figure 4. The arms I, I, the finger I, the hook II,the stop plate I, and the resilient arm I are so formed and positionedrelatively to each other that when the arm I has risen from the positionshown in Figure 2 to that shown in Figure 4 the arms 1 and I have movedfrom the position shown in Figure 3 to that shown in Figure 5 and thelowermost surface II of the finger I contacts with the upper surface IIof the hook II. From this point the arm 1 continues to move towards theposition shown in Figure 7 but upward motion of the arm I is restraineduntil the finger I reaches the edge II of the hook II. (Figure 4 is aside view of the relative position of the elements I, I, I, II, I, I, IIand I2 during the entire period of restraint of the arm I against upwardmotion.) During this interval the switch is still closed. The moment thefinger I passes the edge II of the hook II the restraint on the arm Iagainst upward motion is removed and the arm I instantaneously risesfrom the position shown in Figure 4 to that shown in Figure 6 with theresult that the switch is instantaneously opened. The distance which thearm I rises when travelling from the position shown in Figure 4 to thatshown in Figure 61s that which it would gradually have risen during theperiod that its upward motion was restrained had the restraining elementnot been there. The arms I, I and the hook II are so formed and contactarm I until the metastasis. to otherthat this distancelissuiiicient toinsurethe breaking of the circuit.. sine and arrangement of theseelements: for a; switchto bev used witha particular, motoror piece ofapparatus will of course But,,in the light of my disclosure, theycanreadily be determined bycalculation or simple experimentation by any.one skilled in the art. f 1

the motor cools-the arms 1 and 3 will tend to movein the direction oftheir respective positions showniin Figures 2 and 3. The arms 1 and 3Land the hook it have been'so formed and positioned-that as the arms]and lmove from the position in Figure '1- to that shown in Flaure 3 theupper surface ll of the linger I will pass under thelowersurface "of thehook it assuming mposition-such as illustrated in Figure 8. Asthearm 1continues its movement towards ltspositionshowniln-Figure 3 the arm 3tends to return to its position shown in Figure 2. This motion,howeveryis arrested by reason of the contact between;the,=irpper'surface ll of the finger 3 with the lower surface I! of thehook ll.

' This restraint against motion continues until the ilnger 3, reachesthe edge II of the hook Iii. When the-finger 3 passes the edge l1 of thehook ill the army 3 instantaneously falls from a positionapproximatelythat shown in Figure 6-to approximately that shown in Figure 2 with theresult-that the switch is instantaneously closed. Intermittent openingand closing of the switch during the arm return or return to normalphase tion oi the: arm 1 shown-in Figures "5 and Bis to in: thecircuitli This coil 22' is schematically shown in Figure 2'and1ssoconstmcted that'it pin) of the switch elements is prevented since thearm is positively. retained in the open position. The distance which thearm 1 falls in going from the position shown in Figure 6 to that shownin 'Figure' 2 is that which it would gradually have fallen during theperiod that the arm 1 moves from theposition' shown in Figure 8 to thatshown in Figure 2 ii' such motion had not been restrained. It isobvious'that in the movement .oi'ythe arm] from "the position shown inFigure 2 to that shown in Figure 7, and vice-versa, the

7 finger 3 will traverse the entire width of the hook it from-:the edgel3 totheedge l1 and vice-.versa. It is for thisreason that the posiwillpermit the normal current of the motor to pass'without heatingappreciably. Ii! an abnormal'currentd'ue tooverload or for 'any otherreason passes through it, it will heat up and in' mm affect-the element3f'near' which it is positioned' caining 1' and [to functionin-the-inanner hereinabove described. In

the particular illustrationherein shown it is asthe uri itwiilfbe witha220 volt /4 HP. motor. Thenormafl'current will be 2 amperes 'iheoverload current been fixed.

The switch 9 difl ers from that shown 1 to s in the fact that one of thethermal arms functions to kick the arm 33 falls after leaving the finger33 is switch open. It further diilers from the switch shown inFiguresl'to 8 in the fact that an auxiliary heating coil is incorporatedintothe switch unit as an integral part thereof.

I Referring more particularly to Figure 9 reference numeral 2! denotesthe thermal switch as a unit which iscomposed of a base 23 of insulatingmaterial, a thermal element 21 attached to a bracket 28 which is carriedby the base 23. a spring arm 23 carried by the said bracket 23, aheating coil- 30 positioned near the arms of the thermal element asshown, and a contact carrying bracket 3!. I l I The thermal element 21originally consisted of a flat piece of electricity conducting heatrcsponsive material which had been cut andbentto form the arms 32 and 33pomtion'ed substantially at right angles'to each other as shown. The arm32 terminates at its free end in the flnger 33 and the free end of thearm 33is fashioned into a hook 33. .The arms 32 and 33 are so formed andpositioned relatively to each other that the finger 34 will becooperatively e aged by the hook 33- when the thermal unit is activated.The auxiliary heating coil 33 is so made that it will permit the normalmotor current to pass through without heating but will heat up underabnormal current conditions.

The thermal switch 23 functions as follows:

(Let it be assumed that the thermal switch 23 has been inserted at asuitable point in they motor circuit by means of suitable connections33-41.)

As long as the current which is flowing thmilh the motor circuit isnormal the arm 33 of the switch 23 will be in the position shown by thefull lines in Figure 9. Under such circumstances the current flows fromthe connection 33 throluh the heating coil 30, which does not heat upsince the current is normal, thence through the spring heat up, thisinturn activates the thermal ele-f ment :1 with the result that them :3begins to move downwardly and ouwardly from the pmition shown by thefulllinesinFlgureQtothat shown by .the dot and dash lines inthe saidfigure.

But the arm 33 is so formed and positioned with respect to the arm 32that the lower surface of the hook" will contact with the upper surface,

of the finger. when the hook reaches the plane of the finger. Thisarrests further travel of the arm 33 in the downward direction without,however, interfering with the movement of the said arm in the outwarddirection. Movement of the arm in the outward direction or horizontalplane continues until thebook 33 reaches the outer tion shownby thefull-linesin Figure 9 v shown by the dotted lines in Figure 9 therebybreaking. the "circuit. The distance distance which the arm 33 wouldhave moved in the downward direction or vertical plane the interval thatits motion was arrested had restraint been present.

arm 33 tends to move and closing of the circuit due to vibration duringthe period when the switch elements arereturningtotheirnormalorcloeedpositionsisentirely eliminated.

Referring more particularly to Figures 10 to 14 inclusive, the switch llconsists of a base member of conducting material having an arm 42 formedononeoftheendsthereoitowhichisattachedbymeansottheclamplngplltesllandl'lot conducting material and the screws4. a spring arm I! of conducting material, a thermal unit u ofconducting material and an auxiliary heating coil ll. The elements 42,I, ll, ll, 41 and 4. are properly insulated from each other by suitableinsulating material 0 wherever the same is necessary as shown.

The spring arm 43 has rcontact element llattachedtheretonearoneoftheendathereof which cooperates with a contactll carried by a bracketarmiliormedontheotherendoithe member 42. Thespring arm 48 has also attached thereto near the free end thereof anodule or bumper I! of insulating material whichcooperateswithanarmuotthethermalunitllin the manner hereinafter to bemore described. The thermal element 44 consists or a piece of thermalrespo material which had been slotted and then bent to form the two arms4 and II positioned substantially at right anglestoeachotherasshowninl'igureli; Thearmll has a slot ll formed thereinnear the free end thereof. The arm I4 is so formed and positionedwithrespecttothearmlithatitsi'ree end" is normally received-within theslot I. oi the arm II.

The thermal switch I functions as follows:

As long as the current in the motor circuit is normal current will flowthrough the thermal switch. (Current flows from the lead I, to the arm48. thence through the contacts I. and II to the bracket 82, thence tothe member 42, thence through the connectors II, II to the heating coilll. thence out through the lead II.) If an overload current flowsthrough the circuit it willheat up the auxiliary coil ll which in turnwill activate the thermal element 4 with theres'ultthatthearmllwillmoveinthe direction-willheatupwhenanoverloadcurrentisp :8 r iatis The thermostatic switchll functions lows:-

As long as the current is normal the arm II and the thermal element "arein the position thermostatic element ll, thence through the heatingcoil'llandout thromhthelead II. As soonasanahnormalcun'entappearaintheline ev 1 ems the coil" wheat. This activates the thermostatic elements-l3 andI4 with the result that these elements tend to move from theirrespective positions shown by the full lines in Figures 15- and 16.totheir positions shown by the dot and dash lines in the said figures. Theelements l3 and I4 are so formed and positioned relatively to each otherthat as the element .13 moves inwardly its edge I9- contacts with theedge of the element l4 with the result that downward motionofthe-element I4 is halted until the element I3 passes the edge 03 of theelement 14 when the element I4. instantaneously jumps to the positionshown. by the dot and dash lines in Figure 15 thereby breaking thecircuit. Downward motion of the arm I5 beyond the position shown by thedot and dash lines in Figure is prevented by the stop 15. As the coil I8cools the elements I3 and I4 tend to return to their switch closedornormal positions. The elements "and I4 are so formed and positioned,however, that as the element .14 rises it contacts the lower edge 95ofthe element I3- with the result that the upward motion of the element14 isrestrained until the element I3 reaches the edge 04 of the element14, when .the element 14 instantaneouslyrisesto approximately theposition shown by the full lines in Figure 15 thereby closing thecircuit. (The distance which the element 14 instantaneously rises andfalls is equal to the distance which this element would gradually riseor fall during the period when the motion of this element upward ordownward" was restrained.) I

The switch 90, shown in Figures. 17 to 19, consists of a casing 9| whichcarries the two piers 93-92 which support the thermostatic elements 93,94, the contact elements 95. 90, 99 and I02, and the heating coils I03'and I04. The heating coils I03, I04 are designed to permit the passageof the normal current which the device it is intended to protectrequires and to heat up in the event an abnormal current is present. Thethermostatic element v93 has a slot I05 formed therein and has a fingerI00 formed thereon so as to overhang thesaldslot. The thermostaticelement 94 has attached to the upper surface thereof the resilientcontact carrying arm I" to which are attached the crossbars I00 and Ill.The cross bars I00 and I09 are of electricity conducting material: andare properly insulated fromthearm ill in the=manner well known in theart. The bar I00 has attached to the lower surface thereof the contacts96 and 91 and the bar I09 has attachedto its lower surface the contactsI00 and III. The thermostatic element 94 has attached to the lowersurface thereof the hook III pomtioned so as to normally rest inside theslot I05 as shown by the full lines in Figure 17. when viewed from thetop a in Figure 18 theportion III of the hook H0 is as wide as thethermalelement 94. It is to be noted that the wide surfaces of theelements 93 and 94 are in planes at right angles to each other. and thatwhen, these elements areactivatedby a thermal change they move in-planesat right.

anglestoeachother.

switch 9l is primarily designed for usewithapolyphasemotorbutcanalsobeusedwith a motor wired interchangeablyfor, either 110 or The switch 90 functions as follows:.

A. In use with a two (2) phase motor We that the switch 90 has beendesigned for use with a one-half'horsepower, polyphase motor having two(2) phases. Then the current which will normally flow, in. each phase is2 amperes. The overload current is assumed to be 4.5 amperes. Theheating coils in this case will permit a current up to 4.5 amperes topass through without being affected but will heat up in the event'thecurrent exceeds 4.5 amperes. The leads I I2 and I I9 are'connected toone phase winding and the leads I I4 and H5 are connected to the otherphase winding. When the circuit is'closed, that is under normaloperating conditions, the current flows as follows: In phase 1: from thelead H2 through the contacts 95, 95 to the bar I00, thence through thecontacts 90, 91 to the heating 'coil'I03 thence out through the leadII3. In phase 2: from the lead II4 through the contacts 99, I00 to thebar I09, thence through the contacts I02, IN to the heating coil i 04thence outthrough the lead 5. As soon as an overload current, that is, acurrent of 4.5 amperes or greater, appears in either phase the coil (I03or I04 as the case' may be) of the said phase. will heat up with theresult that the thermal elements 93 and 94 will be activated with theresult that the elements 93 and 94 will tend to assume thepositionsshown by the dot and dash lines in Figures '17 and 18. The book"0 and the finger I00 are so formed and positioned relatively to eachother that as the arm 94 begins to bend to assume the'position shown bythe dot and dash lines in Figure 17fand the arm 93 begins to bend toassume the position shown by the dot anddash lines in Figure 18, theelement III of the hook H0 is still below the lower surface of thefinger I06. -'This structure enablesthe element III to enter the slotI05. As the'arm 93 continues its movement to its ultimate position shownby the dot and dash lines in Figure 18 the upper surface of the elementIII engages the lower surface of the finger I00 for a certainpredetermined period thereby preventing the rise of lines in the saidfigure, thereby breakingthe cir'-,

cuit in both phases. (It is to be noted thatan overload in either phasecircuit will break the circuit-of'both phases.) As the coil cools theelements 93 and 94 will tendto return to their switch closed positions.The finger I05 and the hook I I0 are so formed and positioned relativelyto each other that as the elements 93 and 94 begin to return to theirrespective switch closed positions the lower surface of the-hook elementI I I remains above the upper surface of the finger I00 until the saidfinger has assumed 'a position beneath the said surface of the saidelement III. Thereafter the, said lower surface of the said element IIIcontacts .the upper surface, of the finger I06. for a period terminatingwhen the finger I05 passes the inner edge of the said ele ment III.During this period motion of the element 94 in a downward direction isrestrained and the switch remains open. Assoon as the finger I00 passesthe inner edge of the element III the element 94 d'ropsfromapproximately its position shown .by the dot and dash lines in Flg- 'urelflto that shown by the full lines in the said figure thereby closingall circuits. (The distance which the element instantaneously rises orfails when the restraint to its motion in either donnrddirecu thedistance which this then or fallen Over period otrstnlnt had no 5beenpluent.) Y B. lnwdthulwtorwedmehaamblytor mmmzzooruqm .hm mm m J mmmg 3 mmm m mmmmwmm m m wmmmmmmmm m wm mwmmww mmmmmm mmmmwmmmwmmmmmwmmmmmmwmmm mmmmmmwMm m m. mm mum m N am mmnwmw mm m mmu wmmmm mmm m w m m fix m mmm mwfi mw WWMWMW W W WWWW mm mmmmmw mm Wwmmmwmwmmmmmmmmmmmmw mm wmm mmm um ,w .mmmnmp 5. n mu 0 A8,". .m amfiwmmmm mfimmmmm wmwmmmm Wwmmmwmm wmmwmmm J ...m..., u m n w a 3 m ma.M wmmmmmm m mmm m m mm mmmmmmm m W m wm mm m m mmmm mmm mmm mm MMmmmmmmmm mmmm mm m mm m mmmmm .2. .w. mum," mu m .m u m 1 n m.. w m M mmm wmm m um m mww mmmmwm mm mmwmwm ..u M ummmwmmm m mm mmm zmm Emma w m"m mummy mmm mmm m am mmmmmmmmmmmmmm mmmmmm m um a mmm m m m mmm mm mmmmaw Mmm mmmmmwmmmmmm w mmmwmmm mmmmm m wmmm mmm moves; a hook formed onone of said thermal responsive arms and a finger formed on the other 01said thermal responsive arms, the said hook and finger being sopositioned that the finger will contact with the inner surface of thehook for a certain predetermined period during the cycle terminating inthe movement of one of the said contacts away from the other and withthe outer surface of the hook during the cycle terminating in themovement of the said contacts toward each other thereby permitting themovement of the said non-contact carrying thermal element whilerestraining the movement of the said contact carrying thermal elementfor a certain predetermined period during each of said cycles.

5. A thermostatic switch consisting of a base member; two arms mountedfor movement upon the said base member one of the said arms being made01' thermal responsive material; an electrical contact element carriedby each of the said arms and positioned for cooperative contact witheach other to close the said switch; a second arm of thermal responsivematerial carried by the said base member and positioned for movement ina plane disposed at an angle to that in which the first said thermalresponsive arm moves; cooperating means carried by each of the saidthermal responsive arms for permitting the movement of the saidnoncontact carrying thermal element while restraining the movement ofthe said contact carrying thermal element for a certain predeterminedperiod both during the cycle terminating in the movement of one of thesaid contacts away from the other and the cycle terminating in themovement 01' one of said contacts towards the other; and a heating coilposi- 6. A thermostatic switch consisting of a base I member; two armsmounted for movement upon the said base member one of the said armsbeing made of thermal responsive material; an electrical contact elementcarried by each of the said arms and positioned for cooperative contactwith each other to close the said switch; a second arm of thermalresponsive material carried by the said base member and positioned formovement in planes disposed substantially at right angles to each other;cooperating means carried by each of the said thermal responsive armsfor permitting the movement of the said noncontact carrying thermalelement while restraining the movement of the said contact carryingthermal element for a certain predetermined period both during the cycleterminating in the movement of one of the said contacts away from theother and the cycle terminating in the movement of one of said contactstowards the other; and a heating coil positioned for activating the saidthermal responsive elements, the said heating coil being formed ofmaterial which will permit the ready fiow of the normal current which isintended to flow through the device to be protected by the saidthermostatic switch but which will heat up upon the presence of anoverload current.

HEINRICH WEIRICH.

